Behaviour
Thecosomata beat their wing-like parapodia to "fly" through the water. They are holoplanktonic; that is, they spend their whole life in a planktonic form, rather than just being planktonic during the larval stage, as is more commonly the case in many marine gastropods, whose veliger larvae are part of the meroplankton.
Little is known about the behaviour of sea butterflies, but they are known to have a peculiar way of feeding. At times, they just float along, ventral-side up, with the currents. They are mostly passive plankton feeders, but at times they can be active feeders. They are generally herbivorous, entangling planktonic food through a mucous web that can be up to 5 cm wide, many times larger than themselves. If disturbed, they abandon the net and flap slowly away. When descending to deeper water, they hold their wings up. Sometimes, they swarm in large numbers and can be found washed up in flotsam, especially along the coast of eastern Australia.
Read more about this topic: Sea Butterfly
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—T.S. (Thomas Stearns)
“The methodological advice to interpret in a way that optimizes agreement should not be conceived as resting on a charitable assumption about human intelligence that might turn out to be false. If we cannot find a way to interpret the utterances and other behaviour of a creature as revealing a set of beliefs largely consistent and true by our standards, we have no reason to count that creature as rational, as having beliefs, or as saying anything.”
—Donald Davidson (b. 1917)
“I cannot be much pleased without an appearance of truth; at least of possibility—I wish the history to be natural though the sentiments are refined; and the characters to be probable, though their behaviour is excelling.”
—Frances Burney (1752–1840)